#168 : SKIP UPGRADE CHECK Utilize the new CI RDS database in CI package pipelines

General MR

Summary

This MR migrates the mattermost package away from using the builtin bitnami postgres module to utilising the new CI RDS database instance exposed by the pipeline.

Relevant logs/screenshots

Clean install passes, showing this works with the provided CI RDS database. The upgrade step fails, which is expected; there is no graceful upgrade path from the builtin bitnami postgresql module to the CI RDS database.

Linked Issue

#168 (closed)

Upgrade Notices

The builtin bitnami postgresql database is no longer enabled by default in the test values or the examples. We do not recommend this configuration. For local development usage where the builtin bitnami postgresql database is desired, set postgresql.install: true and postgresql.auth.sslmode: disable in your values.